Every year occur in the world countless cases of hospital admissions due to toxic food infections, resulting from the presence of microorganisms.
For its part, the twenty-first century consumers demand food with high sensory quality and high nutritional value, that is, minimally processed, to the detriment of conventional products. It is obvious that the application of less drastic processing conditions leads to an increase in microbiological risks and therefore, the variability of microbial behavior becomes critical, as the real possibility of survival and development of the residual microbes in any product has to be known, in order to accurately determine their useful life or the microbiological hazards that the producer is willing to assume.
The study of the incidence and prevalence of pathogens in food is in fact one of the priorities of the European Union in terms of food safety. Its purpose is to assess which are the risks actually involved in food, as well as the adoption of microbiological criteria and food security objectives for some types of food.
Currently there is no material marketed with natural compounds that is able to visually detect the presence of a wide range of microorganisms in packaged products. Therefore, neither the consumer nor the retailer or distributor may determine if the packaged products are contaminated or not by microorganisms. In the case of pathogen microorganisms this situation poses a serious health risk. In order to control them it is necessary to resort to microscopic examination and microbiological analysis or planting in selective culture media, thus involving a large consumption of manpower and material. Furthermore, these methods are destructive, thus implying that the analyzed product is no longer available in the commercial chain; they are extremely time-consuming, since from the time the planting is carried out until the microorganisms count is made, there are between 2 and 7 days, regardless of the time needed for pre-enrichment. Such tests also involve significant laboratory cost. In any case, these tests are randomly performed for a representative number of samples, but in no case they can be made for all units of all food items, whereby there is always a potential risk of microbial contamination in a product and not be detected by the producer or final consumer. In pharmaceuticals the risk is much higher, as it is only detected that there has been a problem of this nature when the damage has already been caused, often irreparable.
In recent years, food packaging systems have evolved in response to consumer demands in terms of expiration, preservation of their properties, freshness, appearance, etc. On the one hand, modern marketing methods demand an attractive packaging which communicates something to the consumer in order for him/her to purchase the product. Secondly, the packages have been evolving over the years in response to the profound changes in the lifestyle, and the packaging industry has had to respond to these changes.
The packages have to perform, among others, the following functions:                hold food,        protect food from physical, chemical and microbiological actions        preserve food quality and healthiness,        prevent frauds,        conditioning the product for commercial handling,        display and identify the product,        inform consumers of the characteristics of the food,        extend the useful life, etc.        
Lately, due to new requirements in consumer demand, there have been two new packaging concepts, the active packaging and the intelligent packaging. Active and intelligent packages can be seen as the next generation in food packaging.
Active materials and articles in contact with food are defined according to European Directive 1935/2004, as those intended to extend the shelf life or to maintain or improve the condition of packaged food, and which are designed to deliberately incorporate components that transmit substances to the packaged food or their environment or which absorb substances from packaged food or their environment. In recent years there has been an important development in the field of active packaging, with a large number of publications referring to this subject (Rodríguez, A., Battle, R., Nerín, C (2007) “The use of natural oils as antimicrobial solutions essential in paper packaging. Part II”. “Progress in Organic Coatings 60 (1): 33-38), Rodríguez, A., Nerín, C, and Battle, R (2008). “New cinnamon-based active paper packaging against Rhizopusstolonifer food spoilage.” Journal of Agricultural and Food Chemistry 56 (15)), López, P., Sánchez C, Battle, R, and Nerín, C. (2007b). “Development of flexible antimicrobial films using essential oils as active agents.” Journal of Agricultural and Food Chemistry 55 (21): 8814-8824) Gutiérrez, L, Sánchez C, Battle, R.; Nerín, C. (2009). “New antimicrobial active package for bakery products.” Trends in Food Science & Technology 20 (2): 92-99.
As for intelligent packaging, the aims are different, and this justifies their separation with a special designation. Their action enables a dream in modern world consumer pretensions, with the packaging itself speaking of the quality of the product it contains or events that have marked his processing, acting as an informer of a possible spoilage or degradation as well as of and inadequate maintenance, transportation or distribution. According to the Directive 1935/2004, intelligent packages are defined as those materials that control the condition of packaged food or their surrounding environment.
As “smart packages” will be classified those who use, either the properties or the components of food or of some packaging material as indicators of product quality and history; so far they are essentially time-temperature indicators, microbiological quality indicators, oxygen or carbon dioxide indicators.
The intelligent packaging is therefore defined as one that monitors the condition of packaged food by providing information on the quality of the packaged food during transport and storage, said food condition meaning:                physiological processes (respiration of fruits and fresh vegetables)        chemical processes (lipid oxidation)        physical processes (hardening of bread, dehydration)        microbiological aspects (damaged by microorganisms), and        infection (by insects)        
These packages are of great interest in food industry and proof of this is that a great deal of effort is currently being done in the development and research of this type of packaging.
Within this group there are the packages that carry labels, dyes, or enamels, which are used as indicators of the quality, safety or treatment of the packaged product. They are based on physicochemical, enzymatic reactions or others, generally leading to a change of color in the device, thus indicating the harm or change that took place in the food.
Thus, the possibility of using the interaction between food and packaging as something positive can begin to be exploited, i.e., by blocking or inhibiting the causes of food spoilage.
Many of the existing smart indicators are very useful for foodstuff packaging industry, such as time-temperature indicators, package integrity, microbial growth, authenticity of the package, and so on. Several of these are proprietary systems but only a few are commercial, most notably the time-temperature indicators.
There are not so many references relating to the development of smart packages that are able to quickly and efficiently detect the presence of microorganisms in the food at the time of its acquisition or intake. Given that the ingestion of spoiled food from the microbiological point of view is one of the biggest causes of health disease (food poisoning), it is important to detect early, i.e., before intake, packaged products that are infected. Thus, the seller can remove them on time and consumers can avoid their intake without risk to health.
The developments disclosed in relation to this type of smart packages, require direct contact between the microorganism and the sensor, which acts as a smart package, such as in patents EP1326653, WO03093784, WO2008026119, (Kimberly-Clark Worldwide, INC), wherein a chromogenic detector is used, or WO0013009, (Johnson Matthey Public Limited Company), wherein metal complexes are used as reaction supports. In document Desbordes, J: CONIVE, L Prevot. A. Annales Francaises Pharmaceutiques 1972, 30 (7-8), 507-518 vanillin colored reaction in sulfuric and phosphoric acid is used to identify the presence of lipids in bacterial studies, and finally identifying the fatty acids by thin layer chromatography and gas chromatography. Again, in this development, the direct contact between the bacterium and the reagent is necessary to produce the reaction. Further, the manufacturing system of this type of sensors is of great complexity, which makes difficult its manufacture on an industrial scale. Moreover, the actuating mechanism is complex and requires first the generation of a colored compound, which will disappear when contacting microorganisms. In addition, the compounds used as chromogens, are chemical compounds that in some cases require special conditions such as acidification, or complex chemical compounds in order for the reaction to take place, several of which cannot be used today in contact with food or have a major limitation in their concentration. In any case, natural compounds are used as main chromogenic compounds, much less compounds accepted as a food additives, with the technological and health benefits this entails.
In view of the deficiencies of the packages so far described, the authors of the present invention, after considerable research, have developed a new material which comprises a partially polar adsorbent solid support impregnated in a solution of vanillin that can be used as colorimetric sensor for the detection of microorganisms in packaged products of different nature.
Advantageously, vanillin (3-methoxy-4-hydroxybenzaldehyde), authorized as a food additive, can detect the growth of microorganisms through a simple and easily identifiable chromogenic reaction. It also acts on the sensor without having to be in direct contact with the food or packaged product, however to take place it needs the presence of a small concentration of moisture in vapor phase.
Vanillin is a natural compound found in many vegetables, especially in vanilla pod. It is industrially obtained from eugenol, the main constituent of clove oil. It is also obtained by oxidation of lignin, a complex polymer found in woody tissue of plants.
Vanillin is widely used as a flavoring agent in foods, especially in pastry. It is also used in the pharmaceutical industry as a gastric stimulant and in perfumery.
There are some references in the state of the art which also cite the use of vanillin as a precursor of other reagents, but it needs a long synthesis process and mixing with solvents such as ethanol and reagents such as concentrated hydrochloric acid, piperidine, methyl iodide or others. For example, in document WO2008026119, vanillin is not the major component of the invention, but it requires the presence of another compound in the reaction for the color change to take place.
Other methods, using vanillin as a detector of the presence of microorganisms need to strongly acidify the medium with HCl, with the drawbacks that this entails, and also they are only able to detect the presence of those microorganisms that are capable of producing indole. Thus, document Ferlin, H. J. and Karabiner (J.V. Euclides 1954, 14, 345-353) discloses a medium containing tryptophan as a source to isolate E. coli and P. vulgaris from mixtures based on differences in the production of indole from tryptophan. With that, they also developed a reagent for performing the indole test. Under these conditions, they used the addition of a 0.25% vanillin solution in concentrated hydrochloric acid to produce a violet color with indole, by direct contact and in liquid phase. That is, indole producing microorganisms were to be found in said solution, producing the indole that gives rise to the chromogenic reaction.
In the light of these drawbacks, one of the main advantages of the present invention is precisely the use of a not harmful natural compound, food additive, such as vanillin, and the capacity to detect the presence of microorganisms without the need for a direct contact between the microorganism and the packaging material.
Its application is aimed at solving a problem that poses a great risk to society, as is the presence of pathogenic microorganisms in food, cosmetics and pharmacy products, or other packaged products.
The material of the invention is incorporated into the packaging material of food, or any other products susceptible to contamination by microorganisms, so that by an easily recognizable color change (from colorless to purple), the consumer is able to reject the product and avoid the food intake or the use of products infected and contaminated with microorganisms harmful for health.
On the other hand, it is a system that greatly contributes to the quality control of packaged goods by timely removing contaminated batches, thereby preventing them from reaching the final consumer as well as all the problems and costs incurred by potential returns. The sectors involved in the development and implementation of this new device would be on one hand the packaging industry, which would be responsible for manufacturing and placing on the market the material incorporated in the package, and on the other hand, the food, cosmetic or pharmaceutical industries. This sector has to deal with the optimization of location of the material inside the package, taking into account the industrial packaging process, in order to achieve a location easily visible to the end user and which does not interfere with the packaged product or impedes the industrial packaging process.
The main advantage of using a sensor such as the one presented as invention is the possibility that it offers the consumer to know that the food he or she is about to eat or the product he or she is about to use is free of microorganisms, at the time of the acquisition and ingestion thereof and thus he or she can refrain from consuming it and reject the product.